From World Pipelines, November 2019
Oil India Limited is the oldest oil and gas company in India and, since it is a company with considerable history, it has many aged and ageing pipeline assets. This article provides an overview of one of the company’s pipeline coating rehabilitation projects that is currently underway. The pipeline in question is the Duliajan Barauni Crude Oil Pipeline – it is 1157 km in length and was commissioned in 1962. In addition, the project includes the 249 km Numaligarh Siliguri Product Pipeline and 9 km of the associated loop lines. The total length of pipeline to be covered in the project is approximately 1415 km of 14 in. and 16 in. diameter steel pipe, with the project due to be completed over a number of years.
The crude oil pipeline
The pipeline runs through three states in India – in the Northeast and Eastern segment of India via Assam, and in West Bengal and Bihar. The pipeline was originally coated with coal tar enamel (CTE)
and, after an extensive coating assessment study in 2014 by an independent agency, it was observed that the coating had lived its life and was showing significant deterioration. However, the steel remained in good condition and there was no sign of external corrosion, such as pitting corrosion, or any loss of wall thickness. Therefore, based on the recommendation of the independent agency, the technical team of Oil India decided that a coating rehabilitation programme was required in order to extend the life of the pipeline by at least 30 years.
The entire rehabilitation programme plan was to complete the work in two phases, with the first phase comprising of 575 km. Tractebel was appointed as the engineering consultant to write the coating project specifications in consideration of the various pipeline routes, geography, environment, and soil conditions. As a company, Tractebel provides a full range of engineering and consulting services throughout the lifecycle of its clients’ projects, including design and project management. It is also one of the world’s largest engineering consultancy companies, with more than 150 years of experience. The second phase for the remainder of the project is expected to be tendered in 2021 or 2022 after phase one has been completed.
The pipeline moves through the Northeastern and Eastern states of India via Assam, West Bengal and Bihar and, since these are areas of high rainfall, they have the challenges of a high water table in many areas. These factors make surface preparation very difficult, so the best solution was not just a single product technology. For areas where surface preparation was more achievable, polyethylene-based cold-applied tapes were specified, whilst for other areas, visco-elastic coatings were chosen. These factors were based on the needs of the project and specific requirements along the pipeline route. In short, the specification called out the following systems in compliance with ISO-21809-3:
- Normal pipeline conditions, meaning dry soil conditions with good accessibility: Polyethylene cold-applied tapes in compliance with ISO-21809-3.
- High water table and areas where blasting could not be undertaken: Visco-elastic based coating systems in compliance with ISO-21809-3.
Choosing ideal systems
After consultation with various coating suppliers and feedback from other pipeline operators, the coating systems that have a successful long-term track record were shortlisted based upon various factors. These key factors included documented long-term performance; complying with ISO coating standards; availability of the materials in large quantities; required manpower to install; accessibility; pipeline route variabilities; surface preparation requirements, and economics.
As a case history, it is useful to look at specific language from the specification. Some of those key elements are detailed next.
Coating materials purchased under this specification are to be used for repair and rehabilitation of hydrocarbon pipelines coated with CTE.
The cold-applied system
The cold-applied polymeric tape shall be applied as a three-layer system consisting of the following:
- Primer (liquid adhesive).
- An inner tape (3-ply) for corrosion protection.
- An outer tape (2-ply) for mechanical protection.
Qualification requirements for the CAT system
In order to qualify a coating system as acceptable for this rehabilitation project, the coating manufacturer shall submit a detailed track record of the offered tape systems that have been used for rehabilitation of hydrocarbon pipelines in India/US/Europe/ME in the last 10 years. Further, the coating manufacturer shall submit a detailed independent test report confirming compliance to all the properties and requirements listed in this specification as per ISO21809-Part 3 2016. The test report shall cover all the properties as listed in this specification and shall be witnessed by international reputed certification agencies like Bureau Veritas, ABS, LRS, RWTUV, RINA, or issued by independent test laboratories. The test report shall not be older than five years from the date of the tender. Production facility from where the coating material is produced may be subjected to inspection by the owner/PMC prior to finalisation of the award.
Coating manufacturer’s training and supervision
The coating manufacturer (to whom order will be placed) shall provide assistance for the following:
- Demonstrating proper method of application of coating systems.
- Conducting procedure qualification trial (PQT) as per ISO 21809 Part 3 2016 Clause 7 ‘Application procedures and qualification’ subclause 7.3. This is required to ensure correct use of coating material and to train applicators of the nominated coating contractor. The PQT will be undertaken on mock up pipes supplied by the owner. Coating tests as specified shall be conducted in the field/nominated test laboratory under witness of PMC quality/inspection personnel.
- Conducting pre-production testing (PPT) as per ISO 21809 Part 3 2016 Clause 7 ‘Application procedures and qualification’ subclause 7.4 on actual pipes to verify surface condition of the pipe after surface preparation; verifying the application of the filler on uneven surfaces; application/consumption of primer, inner wrap and outer wrap coating application with the required overlap and tension; qualification of coating applicators and PMC inspectors who will be deployed in the field. Coating tests as specified shall be conducted in the field under witness of PMC quality/inspection personnel.
Supply history to be furnished by the bidder
The bidder has to provide the supply record of the offered brand of coating material to the hydrocarbon pipeline operator during the last 10 years, indicating the details from Table 1. The information needs to be supported with a copy of purchase orders and performance certificates from end users.
The visco-elastic system
The coating system shall conform to the functional requirement listed in Tables 1, 2 and 3 of the specification when applied on St-2/St-3 wire brush cleaned steel surfaces. The applied thickness of the coating shall be 2 – 2.5 mm.
- Inner wrap: Non-crystalline (fully amorphous), low-viscosity (non-cross-linked), non-reactive, polyolefin fabric reinforced based compound to be applied on St-2/St-3 cleaned steel surface.
- Outer wrap PE/PVC: The outer wrap shall be a 2-ply tape manufactured from polyethylene (PE) or polyvinylchloride backing (PVC) with a laminated pressure-sensitive adhesive on one side. The outer layer tape shall be fully compatible with the properties of the inner wrap. The PE/PVC outer wrap shall be applied spirally with 50% overlap and shall bond effectively to the inner wrap and to itself at the overlaps.
Documentation and evaluation
In order to qualify a coating system as acceptable for this rehabilitation project, the coating manufacturer needed to submit a significant amount of information backed up with documents from previous projects and independent test reports. The production facility where the coating material was to be produced was also subject to inspection by Oil India prior to finalisation of the award. These types of requirements ensure that the asset owner can be confident in the chosen supplier.
Ultimately, after a rigorous technical and commercial evaluation, Seal for Life Industries was chosen as coatings supplier for the project, based on the following:
- Coating products complying with ISO 21809-3.
- Products complying to Tractebel’s specification.
- Extensive major project track record within India and globally.
- Positive feedback from Indian and global pipeline end users and operators.
Seal for Life Industries secured the orders for both the coating technologies and is currently supplying the same. The supply included coating of 680 000 m2 of bare pipe surface area with Polyken’s cold-applied tape system and 37 000 m2 of bare pipe surface area with the Stopaq’s visco-elastic coating system. The systems consist of:
- Cold-applied tape: Polyken 1027 liquid adhesive, Polyken 942 inner wrap and Polyken 955 outer wrap.
- Visco-elastic: Stopaq CZH and Stopaq Outerwrap PVC.
- Oil India specified near-white metal grit blasting (SA2 ½) for dry areas where cold-applied tapes were to be used, and wire brushing (ST3) for areas where visco-elastic coating was to be applied.
The points to take away from a project such as this are:
- The track record of cold-applied tapes is extensive, and they are highly valued on major pipeline coating rehabilitation projects.
- Suppliers who can demonstrate that track record with hard evidence of performance and as a supplier to major projects is critical.
- Alternative technologies of wrap-type systems to accommodate variations in geographical or environmental challenges are available.
This project stands out as a prime example of amalgamating different coating technologies on the same pipeline, based on its trajectory and soil strata.
Certainly, projects such as this one require a supplier who is financially stable, has high-quality technical products, depth in manufacturing capabilities, and technical resources to ultimately support the end user customer’s needs. Seal For Life is proud to be a part of this project and its ongoing relationship with Oil India.